I am an associate professor in the Dept of Oceanography, Texas A&M University. My research is focused on numerical simulation of flow in estuarine, coastal, and continental shelf environments; applications include examining plankton bloom dynamics, formation and destruction of continental shelf hypoxia, and real-time surface current forecasting.

PROJECTS

Buoyancy driven flow in the coastal ocean

RIVER PLUMES

River plumes are a ubiquitous feature of coastal ocean flow. They are regions of strong gradients in both physical tracers and biological properties. I am involved in a study of the Merrimack River plume that investigates, through field measurements, laboratory experiments, and numerical modeling, how the energetic outflow from the Merrimack River estuary transitions to a broad-scale, geostrophic coastal current.

An animation of surface salinity from a numerical simulation of the Merrimack River plume.

Animations of surface salinity in over the Texas-Louisiana shelf over seventeen years.

ESTUARIES

I have had a number of publications that have investigated the processes that influence circulation in estuaries. This work has focused primarily on understanding salt intrusion length- and time-scales, and the processes controlling estuarine exchange rates.

Circulation on the Texas-Louisiana continental shelf

I have a number of projects based on understanding and predicting circulation over the Texas-Louisiana continental shelf. The Texas-Louisiana shelf is a broad shelf with strong buoyancy forcing from the Mississippi and Atchafalaya rivers. Seasonal wind patterns cause the fresh water from these rivers to pool up south of Louisiana in the summertime, and to flow downcoast along the Texas coast during the rest of the year.

SEASONAL HYPOXIA

Seasonal hypoxia forms in near-bottom waters over the Texas-Louisiana shelf in late summer. My research involves examining the influence of physics on the formation, maintenance and destruction of seasonal hypoxia. I have demonstrated that there are different regions along the shelf in which the processes that form hypoxia are distinct. This work is funded by the National Oceanic and Atmospheric Administration.

Selected publications:

Hetland, R. D. and S. F. DiMarco, (2008) How does the character of oxygen demand control the structure of hypoxia on the Texas-Louisiana continental shelf? J. Marine Systems, 70, 49-62, doi:10.1016/j.jmarsys.2007.03.002.
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SURFACE CURRENT PREDICTION - OIL SPILL RESPONSE

We run a nowcast/forecast model of wind-driven circulation over the Texas-Louisiana continental shelf for oil spill trajectory modeling. We use predicted wind fields (the NCEP ETA model) to drive a circulation. This work is funded by the Texas General Land Office.

HARMFUL ALGAL BLOOMS

Harmful algal blooms (K. brevis) occur nearly every year off the coast of Florida, but only sporadically off the coast of Texas. We are using numerical simulations of circulation over the Texas-Louisiana shelf to understand the formation of K. brevis blooms along the Texas coast. Our hypothesis is that downwelling wind events may concentrate K. brevis along the coast, and lead to bloom formation.

TOOLS

ROMS

ROMS is an open-source, community ocean model. ROMS uses a horizontal, curvilinear C-grid and a stretched vertical coordinate. In addition to the core hydrodynamic engine, ROMS has many additional packages for calculating biogeochemical processes, sediment transport. I have been using ROMS for nearly a decade, and have contributed to the code base by adding riverine fresh-water fluxes.

Python

Python is a high-level scripting language, similar to perl or matlab. Python has powerful numerical computing packages, primarily based on numpy/scipy that make it ideal for scientific computation and analysis. For visualization, I use the matplotlib package. In many ways, Python is as simple to learn and as powerful MATLAB, both in terms of computational ability and speed as well as visualization. However, Python is based on a more powerful, object-oriented programing language. For more information, see my Python page.

Cluster computing

I maintain a number of high-performance cluster computers. These machines are either Intel or AMD processors, and are connected with Infiniband. I have purchased my most recent clusters from Advanced HPC. Links to the ganglia pages for each cluster: